This invention relates to a linear, permanent mould casting system and method of casting. The system according to the present invention may produce up to twenty-five different castings simultaneously and does not require as noisy and dirty a casting shakeout system as conventional sand moulding vastly improving foundry working conditions. A casting yield of a permanent mould process in accordance with the present invention is approximately ninety percent compared with seventy-five percent for a disamatic system. At a two million B.T.U. per ton energy requirement, permanent mould casting in accordance with the present invention is seventeen percent more efficient.
In a permanent mould system according to the present invention the mould walls are rigid and inert which not only improves casting yield but improves surface finish and dimensional control. Tolerances of plus or minus one sixty-fourth of an inch are possible which can reduce secondary machining considerably or in some cases even eliminate the operation.
There are disadvantages of known forms of permanent mould castings and in particular due to a rapid cooling rate, permanent mould castings are subject to chilling or the formation of iron carbides. This greatly reduces casting machinability. Additionally, permanent mould dies are expensive and have a definite life span.
The present invention provides great improvements over known systems in the provision of a casting machine or system which transports the permanent moulds through core setting, pouring and knockout stations. This reduces manpower costs substantially and also provides a reduction of in-plant pollutants which then are concentrated in one area and can be cleaned efficiently.
By pouring the castings in a designated area the molten iron can be innoculated just prior to pouring. Due to the fading effect of additives (magnesium, ferro-silicon etc.) the molten iron should be treated just prior to pouring which is only possible if the process utilizes a central pouring station in accordance with the present invention.
Permanent mould castings can be control cooled according to the present invention by being held at 1700.degree. F. to 1800.degree. F. for a short period of time (approximately fifteen minutes) immediately after solidification. This provides sufficient time to allow graphitization or reduction of chill to occur and yet the short holding time prevents warpage. An added advantage of this softening method is a substantial saving in energy in not having to bring the casting up to temperature and hold it there for several hours as is the case in the prior art. This method utilizes the removal of castings from the permanent moulds at a centralized location and the feeding thereof directly into a controlled cooling facility.